1. Field of the Invention
The present invention relates to an image pickup optical lens assembly, and more particularly to an image pickup optical lens assembly comprised of five lens elements and applied to an electronic product, and the optical lens assembly has the features of a short total length and a low cost.
2. Description of the Related Art
As science and technology advance, the development of present electronic products such as digital still cameras, web cameras, mobile phone cameras tends to have a compact design. In addition, users not only require an optical lens assembly with compact design and low cost only, but also need an optical lens assembly with the features of good image correction capability, high resolution, and high quality of images.
In general, a conventional optical lens assembly of a mini electronic product comes with different designs including the two-lens, three-lens, four-lens, and five-lens design. However, if the image quality taken into consideration, the optical lens assemblies with the four-lens and five-lens designs have advantages on aberration correction and modulation transfer function (MTF), and the resolution of the five-lens design having a higher than the four-lens design is applicable for electronic products of high video quality or high pixel requirement.
In various five-lens designs, an optical lens assembly with a fixed focal length and different combinations of positive or negative refractive powers are adopted. As disclosed in Japanese Pat. Publication Nos. JP2003-131136 and JP2005-266771, a cemented doublet lens is used for shortening the total length of the optical system. As disclosed in Japanese Publication Nos. JP2003-185917 and JP2006-293042, U.S. Pat. Nos. US2004/0196571 and US2003/0117722, and R.O.C. Pat. No. TW M313781, a group of stacked lenses is adopted to achieve the wide angle effect. As disclosed in Japanese Pat. Publication No. JP2003-161879, the fourth and fifth lens elements with different refractive powers are used to constitute the optical system, but the total length is too long and inapplicable for the use of the mini electronic devices.
The optical lens assembly for electronic products such as digital still cameras, web cameras, mobile phone cameras requires a compact design, a short focal length, and a good aberration correction. In various designs of the five-lens image pickup optical system with a fixed focal length, the fourth lens element and the fifth lens element with different refractive powers and the fourth lens element or the fifth lens element having an inflection point can comply with the design requirements for a better aberration correction and avoid an excess total length. As disclosed in R.O.C. Pat. Nos. TWM313246, TW201038966, TW201022714, and TWM332199, a good aberration correction can be achieved, but the total length of the optical system still cannot meet the application requirements of mini electronic devices. As disclosed in U.S. Pat. Nos. 7,826,151, US2010/0254029, and US2010/0253829, the fourth lens element and the fifth lens element having an inflection point are used for the design of a shorter total length. In these prior arts, the fifth lens element having an inflection point is adopted to correct the aberration and distortion of images, but the refractive power from the fourth lens element to the fifth lens element cannot be enhanced easily under the limitation of a reduced total length of the image pickup optical lens assembly, such that the aberration correction of the fifth lens element still cannot meet the requirement. Therefore, the present invention provides a practical and feasible design to shorten the image pickup optical lens assembly, while using the refractive power of the five lens elements and the combination of convex and concave surfaces to improve the image quality for the application on compact electronic devices, in addition to the effect of reducing the total length of the optical lens assembly.